1. Field of the Invention
This invention relates to a reception antenna for a radio wave marker and, more specifically, to a reception antenna for a radio wave marker which, when installed in a condition in which it is affected by disturbance noises, can reduce the influence of the disturbance noises and receive a radio wave signal from a road-side radio wave marker transmission antenna in a stable manner.
2. Description of the Related Art
FIGS. 9, 10, and 11 are schematic diagrams showing a vehicle driving assisting system utilizing a conventional radio wave marker system. In the drawings, numeral 1 indicates a road, numeral 2 indicates a road-side radio wave marker transmission antenna installed under the surface of the road 1, numeral 3 indicates a vehicle running on the road 1, numeral 4 indicates an engine constituting the motive power source of the vehicle, numeral 5 indicates a bumper, numeral 6 indicates a radio wave marker reception antenna mounted on the vehicle 3, and numeral 7 indicates a cable connected to the radio wave marker reception antenna 6.
Next, the operation of the above system will be described with reference to FIGS. 9 and 11. When, as shown in FIG. 9, the vehicle 3 running on the road 1 approaches the road-side radio wave marker transmission antenna 2, various kinds of driving assisting information necessary for the driving of the vehicle are supplied from the road-side radio wave marker transmission antenna 2. When passing over the road-side radio wave marker transmission antenna 2, the vehicle 3 receives the driving assisting information by means of the radio wave marker reception antenna 6. As shown in FIG. 11, the driving assisting information received is transmitted from the radio wave marker reception antenna 6 to a vehicle-mounted control unit through the cable 7, and the vehicle is controlled on the basis of the driving assisting information.
When mounting the radio wave marker reception antenna 6 in the front portion of the vehicle 3, the mounting of the reception antenna is effected at a position where it is invisible from outside, for example, at a position between the bumper 5 and the engine 4, as shown in FIG. 10, so as not to impair the outward appearance of the vehicle.
The radio wave marker reception antenna 6 in the conventional radio wave marker system, constructed as described above, has a problem in that it receives not only the radio wave signal conveying the driving assisting information from the road-side radio wave marker transmission antenna 2, but also a radio wave such as a broadcast wave set to the same frequency band as the radio wave signal. Further, it receives disturbance noises, such as an ignition system noise emanated from the vehicle engine 4 and a vehicle-mounted apparatus noise generated from an electronic apparatus like a PC mounted in the vehicle. As a result, the reception of the desired radio wave signal from the road-side radio wave marker transmission antenna 2 is hindered.
This invention has been made with a view toward solving the above problem in the prior art. It is accordingly an object of this invention to provide a radio wave marker reception antenna which is not easily affected by the disturbance noises as mentioned above.
In accordance with this invention, there is provided a radio wave marker reception antenna mounted in a mobile body and adapted to receive driving assisting information from a road-side radio wave marker transmission antenna installed under the surface of a road, wherein the radio wave marker reception antenna is formed of a conductive material and equipped with a cover whose lower side is open.
The cover may have a prism-like configuration.
The cover may have a cylindrical configuration.
The cover may have a conical configuration.
The cover may have a dome-shaped configuration.
Further, the cover may downwardly broaden in a fixed direction, and may be mounted in the mobile body such that the broadening direction is the direction of travel.
Further, the cover may be mounted in the mobile body such that it is inclined from the position where its lower side is directed vertically downward to a position where its lower side is directed toward the direction of travel.
Further, the interior of the cover may be filled with a non-conductive material.